Just added. Works as expectred, but I get this:
"Could not convert argument 0 at"
         "onTriggered@qrc:/qml/ElisaMainWindow.qml:82"
"Passing incompatible arguments to C++ functions from JavaScript is dangerous and deprecated."
"This will throw a JavaScript TypeError in future releases of Qt!"

To be clear, you want an action that does only this, rather than having the "previous track" be smart and go to the beginning of the current track unless you're within the first 5 seconds of the track?

Exactly. Press C and start current track.
And I made it. Now trying to figure out what to do with this error.

Actually I made all necessary key changes and enjoy usability =)

Z - prev, X - rwd, C - start current, V - fwd, B - next, Space - Play/Stop

Feel free to submit a merge request with your change!

I submitted already few requests =)

Just added. Works as expectred, but I get this:
"Could not convert argument 0 at"
         "onTriggered@qrc:/qml/ElisaMainWindow.qml:82"
"Passing incompatible arguments to C++ functions from JavaScript is dangerous and deprecated."
"This will throw a JavaScript TypeError in future releases of Qt!"

Solved creating special variable instead using qint64.

I see that I wasted time on github and you prefer only gilab.

Yes, GitHub has a read-only mirror of KDE source code repos, but all the development happens at https://invent.kde.org/